U can try galact powder (usually available in medical stores).. it wil improve the milk supply
And lactare tablets are also good.. but before taking once u check with ur midwife.. I myself tried.. it was very helpful.. I felt like my breast milk supply is super fine.. then I slowly stopped using them...

yes, you can opt for formula .. as I myself having the same issue hence I'm giving formula to my baby.. pls read the instructions properly on the bottle how much quantity has to be there of water and powder.. it's very important for retaining nutrition value in formula... Ok I'm giving Simyl MCT milk powder + Simyl MCT Oil... Lactogen and Pro Nan 1 is also good... but you have to check which powder suits your baby..